1. Field of the Invention
This invention relates to the field of apparatus for creating sealed test chambers externally around pipe sections and similar devices, the seals being such that many thousands of pounds of pressure per square inch may be contained in the chambers.
2. Description of the Prior Art
There exist substantial numbers of prior art patents for apparatus wherein longitudinal and circumferential seals are provided in order to permit a sealed chamber to be defined around a section of pipe. Patents of this type include, for example, U.S. Pat. Nos. 2,255,921 and 3,744,822. However, the constructions set forth in these and other patents are believed to be incapable of containing and sealing fluid pressures anywhere as near as high as those which may be contained and sealed with the present apparatus and seals. It is to be understood that the higher the test pressure the more rapidly and readily a leak may be detected.
It is extremely important that the apparatus be adapted to open and close rapidly to laterally receive a pipe section when the apparatus is in open condition and to seal pressure of such extreme magnitude that even minute leaks will be readily apparent in a short test period.
Insofar as applicants are aware, the only prior art external tester apparatus which has achieved major commercial success in the oil well industry is that described in U.S. Pat. No. 3,371,521 and improvements thereon which are specified in a Notice of Prior Art found in the present application file. Such apparatus, however, is deficient in important respects, one of which is that it requires a unitarily molded complex packer. The packer is such that the fluid in the test chamber only contacts rubber. Such packers are not only complex and expensive to mold but also bulky to ship and store. Furthermore, when one portion of the packer wears out the entire packer must be discarded, it being impracticable or impossible to replace any one portion of the packer. A further disadvantage relative to such packers is that they are sometimes difficult to load into the casings in the field, this being because the as molded packer circumference at its exterior is larger than the circumference of the closed casing at its interior.
In a U.S. Pat. No. 3,975,945 to Hauk and Carstenson, and in our earlier U.S. Pat. No. 4,099,405 there are disclosed leak testers involving seals made of several elements, including pairs of arcuate segments at either end and a pair of strip seals. Such sealing arrangements have a number of advantages, including ready mass production, shipping and storage, ease of mounting in the casing in the field, separate replaceability when worn, and manufacture in small, common molds. It has been found, however, that strip seals of the above-mentioned U.S. Pat. Nos. 3,975,945 and 4,099,405 are not satisfactory for leak testing under certain very high pressures. In particular the use of an indexing bar such as the bar 88 of FIG. 20 of U.S. Pat. No. 3,975,945, which must fit into an indexing slot in the other casing section, inherently requires a certain amount of tolerance in the sliding fit of the bar into the slot. Without some amount of tolerance the bar cannot enter and be removed from the slot as the casing sections close and open. These tolerances provide a space sufficient to permit extrusion of seal strip rubber from the interior of the pressurized chamber under certain very high testing pressures. Further, it is found that the mounting of the strip seals to the casing is difficult since problems are encountered in the field in aligning apertures of strip seal sections and casing for insertion of securing bolts. Problems also have been encountered in sealing of the interconnection between the strip seals and the arcuate seal segments in the arrangements of these patents.
Accordingly, it is an object of the present invention to provide a leak tester having a number of individual and separately replaceable sealing elements and which avoids or eliminates problems referred to above.